For many years now, satellite-aided search and rescue notification has been available using personal locator beacons (PLBs). Cospas-Sarsat, as this service is officially known, utilizes geosynchronous and low earth orbit satellites. This results in a couple of limitations — the need to have a direct line of sight to a transmitter (for the former), and the possibility that multiple orbits may be required to independently establish a position (for the latter). read more